Mixed metal layered hydroxide-clay adducts as thickeners for water and other hydrophylic fluids

ABSTRACT

Novel compositions useful as fluid gelling agents, especially for use in subterranean applications such as drilling fluids, are prepared by reacting an aqueous dispersion of a clay, such as bentonite, with an aqueous gel of a monodispersed mixed metal layered hydroxide of the formula Li m  D d  T(OH) m+2d+3+na ) A a   n , where D is a divalent metal, such as Mg, T is a trivalent metal, such as Al, and A represents other monovalent or polyvalent anions, the formula being described in detail in the disclosure.

FIELD OF THE INVENTION

Thickening of water or hydrophylic solvents by the use of clay-mixedmetal layered hydroxide compounds.

BACKGROUND OF THE INVENTION

There are various reasons for thickening water aqueous, solutions,hydrophylic solvents, and the like, such as for use as water based metalworking fluids, fire control fluids, oil field drilling fluids, foodadditives, hydraulic fluids, water-based paints or coatings, strippingsolutions, and other applications wherein thickening of a liquid orsolution is beneficial.

Water thickening agents, such as guar gum and polyacrylamide are notstable to high shear, hydrothermal treatment above about 250° F. (121°C.), oxidation, bacterial attack, and salts. To make up for some ofthese problems, such additives as bactericides and antioxidants aresometimes required.

Thickening agents or viscosifying agents for aqueous materials, such asdrilling fluids, which involve some form of hydrous aluminum compoundare disclosed, for example in U.S. Pat. Nos. 4,240,915, 4,349,443,4,366,070, 389,319, 4,428,845, 4,431,550, 4,447,341, 4,473,479, and4,486,318. Patents disclosing other forms of aluminum compounds for thesame purpose are, e.g., U.S. Pat. Nos. 4,240,924, 4,353,804, 4,411,800,and 4,473,480. Similar patents disclosing other types of viscosifyingagents are, e.g., U.S. Pat. Nos. 4,255,268, 4,264,455, 4,312,765,4,363,736, and 4,474,667.

These patents deal with the formation of the hydrous aluminum compoundsin-situ. The major disadvantages to such a process are: (1) Theresulting thickened fluid contains copious amounts of reaction salts.This may be undesirable in many situations. For example, in applicationssuch as paints, metal working fluids, or water-based hydraulic fluids,the presence of salt could cause severe corrosion problems. In the caseof oil field drilling fluids, many performance additives do not workwell if salt is present. Thus it is desirable to drill in fresh water ifpossible. (2) The reactions described in the cited patents are runin-situ (e.g. in the mud pit of a drilling rig). Under such conditions,the reaction cannot be adequately controlled and the properties of theresultant thickener may be unpredictable.

Other problems with the use of Al(OH)₃ as a gelling agent for processessuch as oilfield drilling fluids are as follows:

1. Al(OH)₃ gels are known to detrimentally change with time unlesscertain salts such as carbonate salts are present.

2. The rheology of Al(OH)₃ is not very constant with changing pH values.For example, a slurry of Al(OH)₃ may be very thick and uniform at pH 6but at pH 10, which the drilling industry prefers, the slurry collapsesand the Al(OH)₃ settles out of suspension. This creates significantproblems since most drilling operations are run at pH values in therange of 9 to 10.5.

An historically popular thickening agent, especially in drilling mud,has been mineral clays, such as bentonite clay, often used with otheragents or densifiers, such as Fe₂ O₃, BaSO₄, and others. Variations frombatch to batch of bentonite clay and especially sensitivities to ionsand temperature have resulted in erratic results and adjustment of theformulation is often required during use; this hampers the drillingoperations.

Certain forms of crystalline layered mixed metal hydroxides aredisclosed, e.g., in U.S. Pat. Nos. 4,477,367, 4,446,201, and 4,392,979,wherein Li, Mg, Cu, Zn, Mn, Fe, Co, and Ni are part of the layeredcrystal structure. Other metal aluminates are disclosed, e.g., in U.SPat. Nos. 2,395,931, 2,413,184, 3,300,577, and 3,567,472. Thesecompounds are prepared through various reactions includingcoprecipitations, intercalations, acid digestions and base digestions.

In the drilling of oil wells, drilling fluids or "muds" perform severalfunctions:

1. They remove cuttings from the hole.

2. They cool the drill bit.

3. They provide hydrostatic pressure to balance formation pressure.

4. They control ingress of fluids into the formation and protect theformation.

Functions 1. and 3. in the above list can only be performed ifacceptable rheology is present in the drilling fluid. The most desirablerheology that a drilling fluid can exhibit is pseudoplasticity. Thereare several shear zones in the bore hole of a well and the fluid shouldhave varying viscosities in these zones. In the annulus, between thedrill pipe and the formation, the shear rate is approximately 100 to1000 sec⁻¹. At the drill bit the shear rate is between about 25,000 and200,000 sec⁻¹. In the mud pit the shear rate is less than 30 sec⁻¹. Inorder to carry drill solids at low shear rates, a fluid must have asignificant viscosity. However, if the fluid has a high viscosity at thedrill bit, energy is lost in pumping the fluid. Thus, a good drillingfluid should be shear thinning. It is very important that the fluidmaintain this rheology throughout the drilling process. However, manyadverse conditions that typically inhibit the performance of existingdrilling fluids are, various cations such as calcium and magnesium,fluctuating salt concentrations, high temperatures, oxidationconditions, and the presence of bacteria.

Some of the commercially accepted gelling agents that are used inwater-based drilling fluids are polymers such as xanthan gum, guar gumand polyacrylamides. Non-polymer gelling agents are typically clays suchas bentonite and attapulgite. Each of these gelling agents has its ownlimitations. The polymers typically have instability to various salts,they are susceptible to oxidation and bacterial attack, they break downunder extensive shear, and they are thermally stable to only about 250°to 300° F. The most popular clay gelling agent is bentonite. Thismaterial is severely affected by polyvalent cations and is limited toabout 93° C. unless certain thinners are incorporated. However,bentonite cannot be oxidized, and it is completely stable to high shearconditions.

Often, polymeric materials are added to the bentonite dispersions inorder to be able to use less clay. Some of the common bentoniteextenders are polyacrylamide, and Benex,® copolymer which is availablefrom Baroid. In a typical extended bentonite system, the bentonite levelis between 15 and 20 lb/bbl and the extending polymer level is usuallybetween 0.1 and 0.5 lb/bbl. The extended bentonite system is stillsusceptible to problems associated with divalent ions such as Ca⁺², andit is only as thermally stable as the extending polymer. The systems arealso susceptible to bacterial attack and oxidation.

SUMMARY OF THE INVENTION

In accordance with the present invention a novel composition of matteris prepared, consisting of the reaction product of clay mineral, such assodium bentonite, and a mixed metal layered hydroxide. This newcomposition has utility as a gelling agent of, for example, a drillingfluid, or other thixotropic fluid. The mixed metal layered hydroxidecompound has the following empirical formula

    Li.sub.m D.sub.d T(OH).sub.m+2d+3+na)A.sub.a.sup.n,

where

m represents the number of Li ions present;

D represents divalent metals ions; and

d is the number of ions of D in the formula;

T represents trivalent metal ions;

A represents monovalent or polyvalent anions other than OH ions;

a is the number of ions of A in the formula;

n is the valence of A; and

where (m+2d+3+na) is equal to or greater than 3.

These layered mixed metal hydroxides are preferably prepared by aninstantaneous ("flash") coprecipitation wherein soluble compounds, e.g.,salts, of the metals are intimately mixed (using non-shearing agitationor mixing) with an alkaline material which supplies hydroxyl groups toform the mixed metal hydrous oxide crystals. While the empirical formulais similar to previously disclosed compositions, a distinguishingfeature of the present composition is that the crystals are essentiallymonolayer, or one layer of the mixed metal hydroxide per unit cell,which we call "monodispersed" crystals when they are in a liquidcarrier, meaning that they are individual crystals of monolayer mixedmetal hydroxides. These monodispersed monolayer crystals are believed tobe novel.

DETAILED DESCRIPTION

In the above formula, m may be from zero to about 1, most preferably 0.5to about 0.75, when used.

The D metal may be Mg, Ca, Ba, Sr, Mn, Fe, Co, Ni, Cu, Zn, mostpreferably, Mg, Ca, or mixtures of these, and the value of d may be fromzero to about 4, preferably about 1 to about 3 and most preferably about1.

The T metal may be Al, Ga, Cr, or Fe, preferably Al, and Fe, and mostpreferably Al.

The A anions may be monovalent, divalent, trivalent or polyvalent, andthey may be inorganic ions such as halide, sulfate, nitrate, phosphate,carbonate, most preferably halide, sulfate, phosphate, or carbonate, orthey may be hydrophylic organic ions such as glycolate, lignosulfonate,polycarboxylate, or polyacrylates. These anions often are the same asthe anions which form part of the metal compound precursors from whichthese novel crystals are formed.

The liquid which is gelled by the present described novel mixed metalhydroxides may be an aqueous liquid, such as water or aqueous solution,or a hydrophylic organic material such as alcohol or ketone; also adispersion or emulsion comprising an aqueous medium which containsnon-soluble ingredients (either organic or inorganic) in dispersed formcan be gelled by use of the presently described gelling agent. Whereasthe present gelling agent is found useful as a thickening agent forwaterbased metal working fluids, fire fighting fluids, food additives,hydraulic fluids, latex paints, stripping fluids, lubricants, andothers, especially where extreme pseudoplasticity is a desirableproperty, it is especially useful in drilling fluids, whether it be fordrilling oil wells, water wells, or gas wells, including drilling in theocean floor.

A mixture of the selected soluble metal compounds, especially the acidsalts (e.g. chloride, nitrate, sulphate, phosphate, etc.), are dissolvedin an aqueous carrier. The ratios of the metal ions in the solution arepredetermined to give the ratios desired in the final product. Theconcentration limit of the metal compounds in the solution is governed,in part, by the saturation concentration of the least soluble of themetal compounds in the solution; any non-dissolved portions of the metalcompounds may remain in the final product as a separate phase, which isnot a serious problem, usually, if the concentration of such separatephase is a relatively low amount in comparison to the soluble portions,preferably not more than about 20% of the amount of soluble portions.The solution is then mixed rapidly and intimately with an alkalinesource of OH⁻ ions while substantially avoiding shearing agitationthereby forming monodispersed crystals of layered mixed metalhydroxides. One convenient way of achieving such mixing is by flowingthe diverse feed streams into a mixing tee from which the mixture flows,carrying the reaction product, including the monodispersed layered mixedmetal hydroxides of the empirical formula shown in the Summary above.The mixture may then be filtered, washed with fresh water to removeextraneous soluble ions (such as Na⁺, NH₄ ³⁰ ions, and other solubleions) which are not part of the desired product.

The particular transmission electron microscope used in conductingcrystallographic analyses of the subject mixed metal layered hydroxideswas operated at its maximum limits of detection, i.e. a resolution ofabout 8 angstroms. The monodispersed crystals were so thin, with respectto their diameter, that some curling of the monolayer crystals wasfound, making precise thickness measurements difficult, but reasonableestimates place the crystal thickness in the range of about 8 to about16 angstroms for various crystals. During the drying process someagglomeration of the crystals is apparent in the analysis, giving riseto particles which contain a plurality of the monolayer unit cellstructures. Many flat, unagglomerated crystals are detectable in theanalyses. These monolayer crystals are in contradistinction to 2-layerand 3-layer unit cell structures referred to in e.g., U.S. Pat. No.4,461,714.

One method of preparing the mixed metal layered hydroxide composition,however not exclusively the only method, is to react a solution of metalsalts such as magnesium and aluminum salts (approximately 0.25 molar)with an appropriate base such as ammonia or sodium hydroxide inquantities sufficient to precipitate the mixed metal layered hydroxidecompound. For ammonium hydroxide, the most preferable range is betweenabout 1 and about 1.5 equivalents of OH⁻ per equivalent of anion.

The precipitation should be done with little or no shear so that theresultant flocs are not destroyed. One method of accomplishing this isto flow two streams, the salt stream and the base stream, against oneanother so that they impinge in a low shear, converging zone such aswould be found in a tee. The reaction product is then filtered andwashed, producing a filter cake of about 10% solids. At this point ifthe layered mixed metal hydroxide composition has been washed carefullyto reduce the dissolved salt concentration to a relatively low point,for example, 300 ppm. an odd phenomenon occurs. Over a period of time,the filter cake goes from a solid waxy material to an opalescent liquidthat efficiently scatters light. If ionic material is added back to thedispersion, the viscosity increases drastically and the dispersion gels.The rate of "relaxation" is dependent on the free ion oonoentrations inthe dispersion and will not occur if the concentrations are too high.The effect of various ions on the relaxation process differs. Forexample, the relaxation process is more tolerant of monovalent ions suchas chloride ions than it is of polyvalent ions such as sulfate,carbonate, or phosphate.

If the relaxed dispersion is dried, when the solids level reaches about20 to 25%, the material forms a solid hard translucent material that isvery brittle. It can be crushed to a powder, even though it isapproximately 80% water. This solid will not redisperse in water orother hydrophylic solvents. Even if shear is applied with a Waringblender or an ultrasonic cell disrupter, the solids cannot be made toform stable dispersions.

One fruitful method of drying the material is to add a quantity ofhydrophylic organic material such as glycerine or polyglycol to therelaxed dispersion prior to drying. If this is done the resultant drymaterial will spontaneously disperse in water. If a salt is then addedto this dispersion, the fluid will build viscosity in the same manner asthe liquid dispersion. This drying technique does not work ifsignificant quantities of dissolved salts are present in the dispersion.In this case some dispersion is possible, but the resultant fluid willnot build viscosity.

One of the distinguishing features of the presently disclosed mixedmetal hydrous oxides is the fact that upon filtration after the flashcoprecipitation there remains on the filter a gel which is predominantlythe liquid phase with the crystalline hydrous oxides so swollen by theliquid that they are not visible as a solid phase. One might call thegel a "semi-solution" or "quasi-solution" and it has the appearance andfeel of a semi-solid wax. This is in contradistinction to prior arthydrous oxide precipitates which are readily filtered out of liquid as adiscrete particulate solid material. We would not wish to be limited bythis theory, but it appears that the particular crystalline morphologyobtained here permits or causes the imbibing and holding of largeamounts of liquid.

The mixed metal hydroxide may also be composed of either pure mixedmetal hydroxide compounds or physical mixtures of the layered compoundswith themselves or other hydrous oxides of the D or T metals such ashydrous alumina, hydrous magnesia, hydrous iron oxides, hydrous zincoxide, hydrous chromium oxides, and the like.

Even though this disclosure is based largely on the so-called bentoniteforms of clay, it should be noted here that other forms and classes ofclay are within the ambit of the presently claimed invention, such asamorphous clay (e.g. of the allophane group) and crystalline clay (e.g.2-layer, 3-layer, expanding-type, non-expanding type, elongate-type,regular mixed layer type, and chain structure type). For example, anon-exhaustive listing of the clays is as follows:

    ______________________________________                                        bentonite            vermiculite                                              kaolinite            chlorite                                                 halloysite           attapulgite                                              smectite             sepiolite                                                montmorillonite      palygorskite                                             illite               Fuller's earth                                           saconite             and the like                                             ______________________________________                                    

If quantities of the mixed metal layered hydroxide compound are mixedwith an aqueous dispersion of sodium bentonite, having a concentrationas little as 0.5% wt. the viscosity of the resultant dispersion willdrastically increase. The yield point increases dramatically and theplastic viscosity increases only slightly. The lower range of sodiumbentonite may be about 2 lb/bbl (0.6% wt.), and the minimum quantity ofthe mixed metal layered hydroxide required to build significantviscosity is about 0.1 lb/bbl (0.029% wt.). The benefits that areobserved are that the resultant clay mixed metal layered hydroxideslurry is essentially unaffected by varying calcium concentrations; itappears to be thermally stable to at least 400° F. (16 hr. test); itsupports weighting materials such as barite effectively; it iscompatible with common fluid loss control agents such ascarboxymethylcellulose, carboxyethylcellulose, polyacrylates, and thelike; and the viscosity, especially the yield point, can be easilycontrolled with commercial thinners such as lignite and lignosulfonate.

The interaction of the mixed metal layered hydroxide with bentoniteappears to involve an ion exchange phenomenon. Our current theoryconcerning the interaction is the following. It is commonly known thatclays such as bentonite possess structural defects that give rise to netnegative charges in the clay crystals. These charges must be balanced bycations in order to achieve electrical neutrality, giving rise to thecation exchange capacity that is observed with bentonite. In the case ofsodium bentonite which is usually the clay of choice for drillingfluids, the sodium ion balances the charge on the crystal. Our data alsoindicates that there is a significant amount of anion exchange capacityin the mixed metal layered hydroxide compounds that are disclosedherein. We believe that the mixed metal layered hydroxide interacts withthe bentonite by ion exchanging with sodium ions. The result of thisreaction is that there is an increase in the concentration of solublesodium salts in the dispersion. The sodium comes from the clay and theanion comes from the mixed metal layered hydroxide. Since the reactionseems to be an ion exchange reaction, it should be possible to cause itto not occur or to destroy the mixed metal layered hydroxide clayinteraction by substituting an ion or group of ions into the systemwhich have a greater affinity for either the clay or the mixed metallayered hydroxide compound than the respective associated crystal. Suchan ion is phosphate. If phosphate ions are present in the mixed metallayered hydroxide compound, the interaction with the clay does notoccur. If phosphate ions are added to a dispersion containing bentoniteand mixed metal layered hydroxide compounds, the viscosity decreases andthe interaction can be completely destroyed. Other ions that may causethe same effect are organic ions such as lignite, lignosulfonate, andthe like. Some ions that do not significantly decrease viscosities areNa⁺, Ca⁺², Mg⁺², Cl⁻, CO₃ ⁻², HS⁻ and SO₄ ⁻². This is not intended to bea complete list of ions that do not interfere with the interaction butis given only as a means of demonstrating the type of ions that may becompatible with the system.

Since a chemical reaction occurs between the clay and mixed metallayered hydroxide compounds, we believe that a new composition of matterhas been formed. This new composition appears to be a salt in which thecation is a mixed metal layered hydroxide crystal and the anion is aclay moiety. The composition is characterized as a compound in whichboth the cation and the anion are discrete crystals. The compositionscould be referred to as a "crystal salt", or it could be said that inaqueous dispersion, crystal ion pairs exist. This supposition is furthersubstantiated by the fact that the degrees of interaction appears to beassociated with the available cation exchange capacity of the clay thatis being used.

In each of the subsequent examples, the mixed metal layered hydroxidecompound was prepared by coprecipitation. They were then filtered andwashed to produce pure material. This purified product was thendispersed in water containing quantities of clay minerals to build thethickened fluid.

In this disclosure, the following U.S. metric conversion factors areappropriate: 1 gal.=3.785 liters; 1 lb.=0.454 kg; 1 lb./gal.(U.S.)=119.83 kg/m³ ; 1 bbl.=42 gal. =159 liters; lb./ft² ×47.88=1Pascal; 1 lb./100 ft² =4.88 kg./100 m².

The following examples are to illustrate certain embodiments, but theinvention is not limited to the particular embodiments shown.

EXAMPLE 1

A 0.25 molar solution of MgCl₂. AlCl₃ was prepared. This solution wasthen pumped through a peristaltic pump into one arm of a tee. A 2.5molar solution of NH₄ OH was pumped into a second opposite arm of thetee so that the two solutions met in the tee. The product poured out ofthe third arm and into a beaker. The flows of the two solutions werecarefully adjusted so that the product of the coprecipitation reactionwould have a pH of about 9.5. In this situation that amounts to about a10 to 20% excess of NH₄ OH. The reactor product consisted of delicateflocs of MgAl(OH)₄.7 Cl₀.3 suspended in an aqueous solution of NH₄ Cl.The dispersion was then carefully poured into a Buchner Funnel with amedium paper filter. The product was filtered and washed in the filterwith water to remove the excess NH₄ Cl. The dissolved Cl⁻ concentrationwas about 300 ppm. as measured by Cl⁻ specific ion electrode. The filtercake that resulted was translucent, but not optically clear.

The cake was about 9% solids by weight, determined by drying a sample at150° C. for 16 hrs. The cake had the consistency of soft candle wax. Theproduct was analysed for Mg and Al. It was found that the Mg:Al ratiowas essentially 1:1.

Electron micrographic analysis of the product showed tiny platelets withdiameters of 300 to about 500 angstroms. The particles were so thin thatin some cases, they curled. Estimates of thicknesses of these crystalsare about 10 to about 20 angstroms. The maximum resolution on themicroscope is about 8 angstroms. The theoretical thickness of one layerof MgAl(OH)₄.7 Cl₀.3 is 7.5 angstroms. It should also be noted that inthe process of preparing the sample for electron microscopy, thematerial was dried which probably caused a degree of agglomeration,giving rise to particles which contain a plurality of the monolayer unitcell structures.

After sitting undisturbed for about 16 hours, the filter cake had theconsistency of petroleum jelly. After about 48 hours, the material was athixotropic liquid. The relaxation process continued for about 5 days.At the end of this time, the product was more viscous than water but itwas pourable.

A stock dispersion containing 20 lb/bbl of sodium bentonite obtainedfrom Baroid under the brand name Aquagel was prepared and allowed to situndisturbed for 24 hrs. Several dispersions were then prepared from thestock dispersion. Each contained 5 lb/bbl of bentonite and the quantityof MgAl(OH)₄.7 Cl₀.3, described above, was varied from 0.1 lb/bbl to 1.0lb/bbl. The following Table I lists the yield point, plastic viscosity,and 10 sec. and 10 min. gel strengths for each of the compositions, asmeasured using a Fann viscometer.

                  TABLE I                                                         ______________________________________                                        Amount* of Mixed Metal                                                        Hydroxide Added             Gel Strengths**                                   to the Bentonite                                                                             Yield   Plastic  10 sec.                                                                             10 min.                                 Dispersion     Point** Visc. cp gel   gel                                     ______________________________________                                        0.1            -0.50   2.0      0.00  0.00                                    0.3            3.00    3.0      0.25  1.00                                    0.5            10.50   3.0      4.00  5.00                                    0.8            24.50   4.5      9.50  8.00                                    1.0            28.00   6.5      8.00  7.00                                    ______________________________________                                         *Amount is in lb/bbl; 1 lb/bbl = 2.85 kg/m.sup.3                              **Given in lb/100 ft.sup.2 ; 1 lb/100 ft.sup.2 = 4.88 kg/100 m.sup.2     

EXAMPLE 2

A sample of ultra pure sodium bentonite obtained from Baroid, under thebrand name Aquagel Gold Seal, was dispersed in deionized water to make a10 lb/bbl dispersion. This was allowed to sit for 24 hrs. Two 350 mlaliquots of the bentonite slurry were prepared. One contained noMgAl(OH)₄.7 Cl₀.3 and the other contained 1 lb/bbl of the MgAl(OH)₄.7Cl₀.3 described above. A 350 ml. sample was also prepared that containedonly 1 lb/bbl of MgAl(OH)₄.7 Cl₀.3 and no bentonite. Next, each of thesamples, including a sample that had not been treated with MgAl(OH)₄.7Cl₀.3 were filtered in an API filter press at 100 psi. The filtrateswere placed in acid washed polypropylene bottles. A sample of theMgAl(OH)₄.7 Cl₀.3 and the deionized water that was used throughout theexperiment were filtered through the filter press. After the filtrateswere collected, the solutions were analysed for 27 elements with aLeeman Plasma Spectrometer. The only elements that appeared insignificant quantities were Na, Ca, and Mg. Chloride was analysed byspecific ion electrode and NH₄ ⁺ was analysed colorimetrically. Theresults are tabulated below in Table II.

                  TABLE II                                                        ______________________________________                                                    Concentration, meq/l                                              Composition of Sample                                                                       NH.sub.4.sup.+                                                                        Na.sup.+                                                                              Mg.sup.+2                                                                           Ca.sup.+2                                                                           Cl.sup.-                            ______________________________________                                        Deionized H.sub.2 O                                                                         0.04    0.012   0.014 0.01  0.28                                1 lb/bbl      2.79    0.00    2.24  0.08  3.09                                MgAl(OH).sub.4.7 Cl.sub.0.3                                                   1 lb/bbl      1.16    6.17    0.08  0.08  5.49                                MgAl(OH).sub.4.7 Cl.sub.0.3                                                   and 5 lb/bbl Na                                                               bentonite                                                                     No. of meq of ions                                                                          1.63    0.0     2.16  0.00  0.00                                exchanged on the                                                              Bentonite                                                                     ______________________________________                                    

From the above, the following computations are made: meq of excess Na⁺=/Na/-/NH₄ /-/Mg/=6.17-1.63-2.16=2.38. No. of meq of Cl⁻ ions exchangedfrom the MgAl(OH)₄.7 Cl₀.3 =5.49-3.09=2.40 meq. These data indicate thatsubstantially equivalent amounts of sodium and chloride ions arereleased when the reaction occurs.

It will be understood by practitioners of these relevant arts that theadducts formed in accordance with the present invention will be expectedto have waters of hydration accompanying them unless driven off byelevated temperature of, generally greater than about 100° C.

We claim:
 1. A composite comprising the adduct or reaction product of atleast one mineral clay with at least one monodispersed monolayercrystalline mixed metal layered hydroxide conforming essentially to theempirical formula

    Li.sub.m D.sub.d T(OH).sub.(m+2d+3+na) A.sub.a.sup.n,

where m represents the number of Li ions present; the said amount beingin the range of zero to about 1; D represents divalent metals ions; withd representing the amount of D ions in the range of zero to about 4; Trepresents trivalent metal ions; A represents monovalent or polyvalentanions of valence -n, other than OH⁻, with a being the amount of Aanions; and where (m+2d+3+na) is equal to or greater than
 3. 2. Thecomposition of claim 1 wherein m represents an amount in the range ofabout 0.5 to about 0.75.
 3. The composition of claim 1 wherein drepresents an amount in the range of about 1 to about
 3. 4. Thecomposition of claim 1 wherein d represents an amount of about
 1. 5. Thecomposition of claim 1 wherein D is at least one of group comsisting ofMg, Ca, Ba, Sr, Mn, Fe, Co, Ni, Cu, and Zn.
 6. The composition of claim1 wherein D is at least one of the group consisting Mg and Ca.
 7. Thecomposition of claim 1 wherein D is Mg.
 8. The composition of claim 1wherein D is Ca.
 9. The composition of claim 1 wherein T is at least oneof the group consisting of Al, Ga, Cr, and Fe.
 10. The composition ofclaim 1 wherein T is Al or Fe.
 11. The composition of claim 1 wherein Tis Al.
 12. The composition of claim 1 wherein T is Fe.
 13. Thecomposition of claim 1 wherein A is at least one monovalent orpolyvalent inorganic anion.
 14. The composition of claim 1 wherein A isat least one monovalent or polyvalent organic anion.
 15. The compositionof claim 1 wherein A is at least one monovalent or polyvalent anion ofthe group consisting of halide, sulfate, nitrate, phosphate, carbonate,glycolate, lignosulfonate, polycarboxylate, polyacrylate, and sodiumpolyacrylate.
 16. The composition of claim 1 wherein the mineral clay isat least one of the group consisting of bentonite, kaolinite,halloysite, smectite, illite, montmorillonite, saconite, vermiculite,chlorite, attapulgite, sepiolite, palygorskite, and Fuller's earth. 17.The composition of claim 1 wherein tne mineral clay is at least one ofthe classes consisting of amorphous clays of the allophane group andcrystalline clays of the 2-layer type, 3-layer type, expanding type,non-expanding type, elongate type, regular mixed layer type, and chainstructure type.
 18. The composition of claim 1 wherein the mineral clayis bentonite.
 19. The composition of claim 1 wherein the mineral clay isbeneficiated bentonite.
 20. The composition of claim 1 wherein theweight ratio of layered hydroxide/clay is in the range of about 0.02/1to about 1/1.
 21. A method for reacting a mineral clay with amonodispersed monolayer mixed metal layered hydroxide of the formula

    Li.sub.m D.sub.d T(OH).sub.(m+2d+3+na) A.sub.a.sup.n,

where m is an amount in the range of zero to about 1; D is a divalentmetal ion, with d in the range of zero to about 4; T is a trivalentmetal ion; A represents monovalent or polyvalent anions other than OH⁻,of valence -n, with a being the amount of A anions; (m+d) is greaterthan zero and (m+2d+3+na) is equal to or greater than 3, said methodcomprising reacting, by intimately mixing together, an aqueous gel ordispersion of said layered hydroxide with an aqueous dispersion of theclay whereby metal ions from the clay and anions from the layeredhydroxide go into the aqueous solution by ion exchange of clay anionsfor layered hydroxide anions and whereby an adduct of the mixed metallayered hydroxide and the clay is formed.
 22. The method of claim 21wherein the mixed metal layered hydroxide is MgAl(OH)₄.7 Cl₀.3 and theclay is bentonite.